1. Field of the Invention
This invention relates to an improved stabilized solvent composition. More particularly, this invention relates to compositions, which include a volatile solvent component n-propyl bromide, and one or more non-volatile additives that have the capability of preventing breakdown of the solvent molecules with various reactive metals.
2. Prior Art
The production of many electrical and mechanical parts generally require a final step of cleaning the part prior to final assembly. Traditionally this cleaning process employed chlorinated, fluorinated, or a combination of chlorinated and fluorinated solvents. Such solvents, e.g., 1,1,1-trichloroethane and 112-trichloro, 221-triflouroethane,are not favored today because of environmental concerns,
Recently it has been recognized that n-propyl bromide is an environmentally friendly alternative to these solvents. Its primary advantage is that it can be used in traditional cleaning applications such as vapor degreasing, aerosols, wipes, etc. without any detrimental effect to the environment.
However, like many chlorinated solvents, n-propyl bromide will react with various reactive metals, in particular aluminum and its alloys. N-propyl bromide has an advantage over 1,1,1-trichloroethane, which was traditionally used to clean aluminum parts, in that such reaction occurs at a much slower rate. For example, 1,1,1-trichlorethane will react almost immediately with aluminum whereas n-propyl bromide will only begin to react with aluminum after about 10 minutes of contact time.
Although n-propyl bromide reacts slower in contact with aluminum, the existence of such a reaction, regardless of the reaction time, necessitates the use of various xe2x80x9cstabilizersxe2x80x9d in cleaning compositions containing n-propyl bromide to inhibit the reaction between n-propyl bromide and reactive metals. Many of the stabilizer packages developed to stabilize n-propyl bromide were substantially similar to the stabilizer packages used with chlorinated solvents, in particular those used with 1,1,1-trichoroethane. However, it has been found that many stabilizers that showed efficacy when used with 1,1,1-trichloroethane showed little, if any efficacy in stabilizing n-propyl bromide
Many of the prior art stabilizer compositions suffer from a number of disadvantages, which limit their usefulness for today""s applications. For example, some known volatile stabilized solvent compositions have often proved less than satisfactory due to the ineffective stabilization against water because of their high water solubility, which can come from high humidity conditions. Also, although some known compositions have proven effective to stabilize solvent formulations, they have not been practical in use when solvent losses are minimized. Also, many prior art stabilizer compositions use solvents that deplete the ozone layer, contribute significantly to global warming, are economically unfeasible and/or are too toxic (very low TLVs). Another relatively serious problem associated with the use of known stabilized solvent compositions, which is dependant on the specific application and substrates to be dried, is that such solutions tend to deplete or get used up. This requires the operator to constantly evaluate the solutions resulting in equipment and/or processing down time or worse, if they are not monitored carefully, erosion of the equipment and/or the substrates by the acidic solutions produced. Such acidic conditions can cause corrosion of the cooling and heating coils and inner parts of the machine as well as corrosion of the substrates being treated. Such an unstable situation caused by such acidity interrupts and delays the cleaning process. The equipment must then be drained and all the parts neutralized prior to recharging the system with fresh solvent. Further, the acidified solvent, which is typically caused by the formation of hydrogen bromide, must be neutralized and disposed of properly. U.S. Patents of general interest are:
U.S. Pat. No. 6,048,832 to Thenappan describes azeotrope-like compositions of 1-bromopropane, 4-methoxy-1,1,1,2,2,3,3,4,4-nonafluorobutane (HFE-7100) and at least one organic solvent selected from the group consisting of methanol, ethanol, 2-propanol, 2-methyl-2-propanol, tetrahydrofuran, nitromethane, and methylene chloride and more particularly to azeotrope-like compositions based on these compounds which are useful as solvents in refrigeration flushing, oxygen system cleaning and vapor degreasing applications.
U.S. Pat. No. 6,010,997 to Thenappan et al describes compositions of 1-bromopropane, nitromethane or acetonitrile and at least one alcohol selected from the group consisting of ethanol, 2-propanol and 2-methyl-2-propanol and more that form azeotrope-like compositions which are useful as solvents in refrigeration flushing, oxygen system cleaning and vapor degreasing applications.
U.S. Pat. No. 5,858,953 to Aman et al. describe a 1-bromopropane composition that stays stable even though repeatedly used at high temperatures over an extended period of time as in vapor degreasing. The stabilized 1-bromopropane compositions comprises 100 parts by weight of 1-bromopropane, from 0.1 to 5 parts by weight of nitromethane, and from 0.1 to 5 parts by weight of 1,2-butylene oxide or trimethoxymethane.
U.S. Pat. No. 5,846,923 to Reierson describes a surfactant composition comprising poly (alkylamine bis-ethoyxylate phosphates).
U.S. Pat. Nos. 5,824,162 and 5,616,549 to Clark describe a solvent mixture comprising n-propyl bromide, a mixture of terpenes and a mixture of low boiling solvents, and a method for cleaning an article (e.g., an electrical, plastic, and metal parts) in a vapor degreaser using the solvent mixture.
U.S. Pat. No. 5,792,277 to Shiubkin et al. describes a stabilized cleaning composition that contains n-propyl bromide. The cleaning solvent compositions includes an alcohol selected from 1-propanol and 2-butanol, including mixtures thereof, as a co-solvent so as to form azeotropic or azeotropic-like mixtures which have no fire or flash points.
U.S. Pat. No. 5,707,954 to Lee describes a stabilized solvent composition which is comprised of: a solvent portion which includes at least 90 wt % n-propyl bromide; and a 1,4-dioxane-free stabilizer system which includes 2,2-dialkoxypropane in which each alkoxy group independently contains up to 3 carbon atoms. The solvent composition is useful as a degreaser and cleaner in both cold and vapor cleaning systems.
U.S. Pat. No. 5,690,862 to Moore, Jr. et al. describes a solvent system that is non-flammable. The system comprises a hydrocarbon solvent having a flash point less than about 38xc2x0 C. and another solvent containing at least 90-wt % n-propyl bromide.
U.S. Pat. No. 5,679,632 to Lee et al. describes a solvent system and process for cleaning cellulose triacetate polymer camera film. The solvent system comprises n-propyl bromide and a mix of an alkyl bromide in which the alkyl group contains 4 to 7 carbon atoms and an alkane containing 6 to 7 carbon atoms.
U.S. Pat. No. 5,665,170 to Lee et al describes a non-stabilized or at least only lightly stabilized n-propyl bromide-based solvent system which is suitable for use in the presence of metals which normally and easily catalyze the dehydrobromination of brominated hydrocarbons, such as isopropyl bromide.
U.S. Pat. No. 5,665,172 to Oshima describes deterring solvent that essentially consists of (A) a brominated hydrocarbon of the formula: CnH2n+ 1Br wherein n represents a number of 3 or above and/or a brominated hydrocarbon of the formula: CmH2mxe2x88x921Br wherein m represents a number of 2 or above. The solvent composition comprises the above-described solvent (A) and a stabilizer selected from the group consisting of nitroalkanes, ethers, epoxides and amines.
U.S. Pat. No. 5,514,301 to Bil et al. describes dewetting or degreasing compositions based on halogenated aliphatic solvents containing in solution at least one mono- or dialkyl phosphate of a fluorinated amine, at least one quaternary ammonium mono- or dialkylphosphate and optionally a quaternary ammonium chloride.
U.S. Pat. No. 5,492,645 to Oshima et al. describes a deterging solvent containing a brominated hydrocarbon of the formula: CnH2n+ 1Br wherein n represents a number of 3 or above and/or a brominated hydrocarbon of the formula: CmH2mxe2x88x921Br wherein m represents a number of 2 or above. The composition also contains a stabilizer selected from the group consisting of nitroalkanes, ethers, epoxides and amines. The solvent composition is described as stable, having a deterging effect and usable as a substitute for xe2x80x9cflonxe2x80x9d and chlorine solvents.
U.S. Pat. No. 5,403,507 to Henry describes a solvent mixture for use in vapor cleaning degreasing systems containing dibromomethane, instead of such high ozone depleting chlorofluorocarbons as Freon and 1,1,1 Trichloroethane, mixed with other solvents including a number of low boiling solvents which prevent the mixture from becoming acidic on the release of bromine into the atmosphere.
U.S. Pat. No. 5,256,329 to Li et al. describes drying agent compositions comprising a volatile hydrochlorofluorocarbon such as 1,1-dichloro-1-fluoroethane and demulsifer.
U.S. Pat. No. 4,618,447 to Seelig describes drying compositions comprising a volatile halocarbon and one or more aromatic quaternary ammonium salts of a phosphate ester, and methods of using such compositions for cleaning and/or drying non-absorbent articles.
U.S. Pat. No. 4,594,177 to Lantz et al. describes a demoisturizing composition used for the displacement of liquid water, comprising a chlorofluorocarbon that is liquid at room temperature, and a surface-active agent.
U.S. Pat. No. 4,018,837 to Archer et al. describes a stable 1,1,1-trichloroethane composition containing 1,1,1-trichloroethane, and, as the essential acid acceptor, 0.25 to 1 weight percent of a C4-8 monoepoxide, epichlorohydrin or a mixture of such epoxides and, as the essential stabilizer against metal-induced decomposition, 3.5 to 4.5 weight percent of a three-component system selected from the group consisting of dioxane, trioxane, and dioxolane, t-butyl alcohol, a C1-3 nitroalkane or mixtures of nitroalkanes, in specific proportions. When a nitroalkane is not present as a member of the three-component mixture, it is added in an amount to provide from about 0.25 to 1 percent by weight of said nitromethane. These compositions are said to be stable in the presence of aluminum, zinc, iron, copper and their alloys, both in the liquid and vapor state of the compositions.
U.S. Pat. No. 3,564,061 to Correia et al. describes chlorinated or brominated alkenes containing 2-4 carbon atoms stabilized with trimethyl orthoformate and a compound selected from the group consisting of C1-C4 alkanols, C1-C4 alkyl cyanides, 1,4-dioxane, trioxane and C1-C4 nitroalkanes.
There is therefore a need for an improved non-volatile stabilized solvent composition, which does not decompose in the presence of metals.
It is an object of this invention to provide a stabilized n-propyl bromide cleaning composition that does not suffer from a number of disadvantages which limit the usefulness of the known compositions.
It is a further object of this invention to provide a stabilized cleaning composition that provides effective stabilization against water.
It is still another object of this invention to provide a stabilized cleaning composition that is practical to use when solvent losses are minimized.
It is yet another object of this invention to provide a stabilized cleaning composition that does not deplete the ozone layer or contribute significantly to global warming, is economical to use and is not toxic (very low TLVs).
It is still another object of this invention to provide a stabilized cleaning composition that does not substantially deplete or get used up and does not require constant monitoring during use.
The cleaning compositions of this invention consists essentially of:
about 0.1 to 5% butylene oxide,
about 0.1 to 5.0% t-butanol,
about 0.1 to 5% acetonitrile,
about 0.1 to 5% nitromethane, and the remainder n-propyl bromide.
All compositions are in weight percent.